1. Field of the Invention
This invention pertains to saws of the type which can be quickly and easily collapsed into a compact article.
2. Description of the Prior Art
There are basically three categories of known collapsible saws, a first category being so-called knock-down saws, having frame members and a saw blade arranged detachable in relation to each other. A second category is the type having three-membered frames including a back member and two legs members, the saw blade being held between the free ends of the leg members. A third category of saws includes a straight frame member with a handle pivotally connected to one end of the frame member, arranged to form an angle with a saw blade interconnecting the free end portions of the frame member and the handle, and this is the type of saw contimplated herein.
Examples of this third category of saws are disclosed in U.S. Pat. Nos. 3,245,445 and 3,724,519. The collapsible saw of U.S. Pat. No. 3,245,445 has many advantages, but it is provided with a threaded blade tightening element carrying a wing nut. With this type of tensioning element, there is always an obvious risk of getting the blade so tight that the frame members are bent or subjected to undue stresses, and this risk is emphasized if the user decides to tighten the blade with pliers. Overtightening is far more serious in the case of lighter weight collapsible saws than in the case of solid-membered conventional saws having wingnut blade tightening bolts. A further disadvantage is the offset extension necessary for carrying the tightening element, as well as the short leg portion extending transversely from the end of the handle remote to the offset extension, since these two members extend outwardly from the straight member when the saw is folded together into a non-operative position. When used with multiple saw blades, the blades not selected must be entered into the straight member one at the time. There is obviously also a certain risk that the user quite easily may lose the wingnut, thus making the saw inoperable.
The collapsible saw disclosed in U.S. Pat. No. 3,724,519 includes expanding lever means positioned across the angle formed by the frame member and the handle to overcome the disadvantages of a threaded blade and the handle as replacement for a tightening element carrying a wing nut. The handle, pivotally connected to one end portion of the frame member, is movable between a position extending transversely from the frame member and a position in contact with the adjacent side of the frame member, i.e. a sector in which no movement should occur when the saw is used. As a consequence, the lever means extending across the angle formed by the frame and the handle, is acting as the only element maintaing the angular relationship between the frame member and the handle when the saw is used. The obvious disadvantage of this type of arrangement is the fact, that the handle is only restricted by the expanding lever means from a folding movement directed towards the frame member, and as a result, the saw frame is in no way as rigid as the saw frame discussed with reference to U.S. Pat. No. 3,245,445, in which such a movement can not be performed. Apart from the risk that the saw may collapse during use, or perform unsatisfactorily due to varying tension imposed on the saw blade if the lever means is not maintained rigid, the saw frame is only intended to carry one saw blade within a magazine defined by the frame, and it is obviously desirable to have more than one type of saw blade readily available.